I believe you have to have a minimum of one liter of fuel at anytime during the race. For those who advanced to Q2 and Q3. Normally The stewards would not have time to scrutinize the car between sessions, unless you got knockout in the session. And after Q3, all cars must return to parc ferme in their own power (implemented after Lewis hamilton's pole in Canada 2010 qualifying) and provide a minimum of one liter of fuel sample.
Seriously wtf mclaren shot themselves in the foot again???!!!